Despite significant improvements in ambient air quality over the past 30 yr, air pollution continues to pose a challenge to public health. Case control studies associate ambient ozone (03) levels with reduced lung growth in children, and retrospective review of hospital ER records suggest visits by young and elderly asthmatics are increased due to dyspnea and exacerbation of their airway disease, following increases in ambient 03 levels. The overall objective of this project is to characterize the ozone response phenotype (epithelial permeability and airway hyperreactivity) in healthy and asthmatic subjects and evaluate the association of these selected phenotype(s) with polymorphisms i n candidate susceptibility genes. Based on inflammatory cell influx after 03, published reports have described both high and low responder populations. Our preliminary data also demonstrate after 03 a between-subject differential increase in airway hyperresponsiveness for asthmatic and healthy subjects. Based on these observations, we hypothesize that specific gene polymorphisms/mutations contribute to differential sensitivity of humans to 03-induced airway hyper-responsiveness and loss of epithelial integrity. Aim 1: Determine the inter-relatedness of response parameters (airway hyper-responsiveness and epithelial permeability), and to assess if asthmatic airways are differentially responsive to 03. Aim 2: Assess whether acute lung responses to 03 adapt during re-exposure to 03. We will evaluate subjects with differential sensitivity t o O 3 and r elate t he "acute exposure" p henotype t o the chronic exposure p henotype and determine if these are related or distinct response phenotypes. Aim 3: Determine if selected genetic markers are associated with response by lung airways to 03. The goal is to assess if polymorphic alleles on specific candidate 03 susceptibility genes as determined by mouse modeling and human studies, associate in selected, differentially O3-responsible subjects. The proposed research is applied and our approach has good potential to identify elements intrinsic to lung injury and asthma that are associated with host factors. We have selected loci on 3 candidate susceptibility genes: TNF-alpha on chromosome 6, TLR-4 on chromosome 9, and NOS2 on chromosome 17, and will determine if they associate with sensitivity of healthy and asthmatic subjects to phenotypes of airway reactivity and epithelial permeability. The research aims are innovative in that they represent the interface between epidemiology, population responses, molecular genetics, and environmental toxicology. Since O3-airway epithelial interactions in vivo in the human have only been identified to a limited extent, new information will be gained. The proposed research adheres closely to the theme of the Program Project to investigate the genetic basis of differential responsiveness of the lung to air pollution as a factor in the susceptibility and development and exacerbation of asthmatic airway disease.